/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.druid.msq.statistics.serde;

import org.apache.druid.java.util.common.StringUtils;
import org.apache.druid.msq.statistics.KeyCollectorSnapshot;
import org.apache.druid.msq.statistics.QuantilesSketchKeyCollectorSnapshot;

import java.nio.ByteBuffer;

/**
 * Format:
 * - 8 bytes: {@link QuantilesSketchKeyCollectorSnapshot#getAverageKeyLength()}
 * - 4 bytes: length of quantile sketch snapshot (n)
 * - n bytes: the sketch snapshot
 */
public class QuantilesSnapshotSerializer extends KeyCollectorSnapshotSerializer
{
  public static final byte TYPE = (byte) 2;

  @Override
  protected byte getType()
  {
    return TYPE;
  }

  @Override
  protected byte[] serializeKeyCollector(KeyCollectorSnapshot collectorSnapshot)
  {
    final QuantilesSketchKeyCollectorSnapshot quantileSnapshot = (QuantilesSketchKeyCollectorSnapshot) collectorSnapshot;
    double averageKeyLength = quantileSnapshot.getAverageKeyLength();
    final byte[] sketch = StringUtils.decodeBase64String(quantileSnapshot.getEncodedSketch());
    return ByteBuffer.allocate(Double.BYTES + Integer.BYTES + sketch.length)
                     .putDouble(averageKeyLength)
                     .putInt(sketch.length)
                     .put(sketch)
                     .array();
  }
}
